Vegetable · Solanaceae
Tomato
Solanum lycopersicum
Give it full sun, steady water, and good airflow, and the tomato pays you back all summer.
Full sun
Every 3–7 days
70–84°F · 21–29°C
50–90 days
Overview
Nothing says summer in the garden quite like a ripe tomato. It belongs to the nightshade family and traces back to the Andes, where people grew it long before it spread to the rest of the world. Today it grows almost anywhere as a warm season annual, just as happy in a backyard bed as in a pot on a sunny balcony.
The choices run wide. Some plants stay short and bushy and ripen their whole crop within a week or two. Others climb, sprawl, and keep setting fruit right up until frost. Gardeners call the first kind determinate and the second indeterminate, and knowing which one you have shapes how you prune it and hold it up.
Tomatoes forgive a beginner, yet they reward a little attention. Give them steady water, full sun, and room for air to move, and the fruit comes in sweet and heavy. Cut those corners and you trade flavor for split skins and bare stems.
Care
The short version: full sun, with a touch of afternoon shade where summers run hot. Keep the soil evenly moist with about an inch of water a week, plant in rich, fertile ground, and leave each plant room to breathe.
Light
Tomatoes want 8 or more hours of direct sun a day. A little afternoon shade helps where summers turn brutal, but true shade gives you tall, floppy plants and far less fruit.
Water
Aim for steady, even moisture instead of a soak followed by a drought. That works out to about an inch of water a week, and more during a heat wave or in a pot. Even watering is what keeps the skins from splitting.
Soil
Plant in rich, well drained ground with plenty of compost dug in. A pH of 6.0 to 6.8, a touch on the acidic side, suits them best, and loose soil lets the deep roots run.
Temperature
They grow best between 70°F and 84°F (21°C to 29°C). Fruit set stalls once nights stay warm or days turn hot, and even a light frost ends the plant.
Humidity
Ordinary outdoor humidity is fine, so there's no number to chase. Good airflow matters far more here, since crowded, damp leaves are how most tomato diseases take hold.
Feeding
Give a balanced feed at planting, then feed again once the first fruit sets. Go easy on the nitrogen, or you'll grow a big leafy plant with very little to pick.
Pruning
On the tall indeterminate types, pinch out the side shoots to leave one or two main stems. Leave the bushy determinate types alone, since pruning them only costs you fruit.
Repotting
Move seedlings into roomier pots before they head outside so the roots never coil. Once a plant is in its final bed or large container, it stays put for the rest of the season.
Overwintering
Grow the tomato as an annual. It's a tender perennial at heart, but the first frost finishes it off, so most gardeners just replant each spring.
Size & spacing
Plants run from 2 to 10 feet (60 cm to 3 m) tall depending on the type. Give each one 1.5 to 3 feet (45 to 90 cm) of room so air can move and disease stays down.
When to plant
Tomatoes love warmth and have no patience for frost. Start the seeds indoors in late winter, set the plants out once the cold has passed, and pick fruit from midsummer until the first frost ends the season.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 5–8 weeks before last frost (start seeds indoors before last frost)
- Plant: at last frost to 2 weeks after (after frost, soil ~60°F (16°C))
- Harvest: July–October (midsummer to first frost)January–April (midsummer to first frost)
Hardiness
USDA hardiness zones: 10–11
Temperature: down to -1°C
Troubleshooting
Most tomato trouble shows up first on the fruit or the lower leaves. Learn to read those early signs and you can step in before a small issue spreads. Match what you see below, then act while it still helps.
Greasy gray blotches and a plant that collapses fast
Late blight moves quickly in cool, damp weather and can take down a plant in days. Pull the whole plant, bag it, and bin it. Never compost it, or you hand the disease straight to next year's garden.
Fix:
- Pull and bag plants immediately
- Do not compost
- Preventive fungicide on neighbors
Lower leaves yellow and wilt while the plant fades
A soil fungus such as fusarium or verticillium wilt clogs the stem from the inside, and there's no cure once it sets in. Pull the plant and start fresh next season in a container of clean mix, or choose varieties bred to resist it.
Fix:
- No cure; remove plant
- Grow in containers with fresh mix
Dark, sunken patch on the bottom of the fruit
This is blossom end rot, and it comes from uneven watering rather than poor soil. When a plant dries out and then floods, it can't move calcium into the fruit. Water on a steady schedule, mulch to hold moisture, and pull off any fruit that's already marked.
Fix:
- Maintain even soil moisture
- Mulch root zone
- Remove affected fruit
Brown rings like a bullseye on the lower leaves
This is early blight, a fungus that thrives in warm, wet weather and starts low on the plant. Snip off the spotted leaves, open the plant up for better airflow, and keep water off the foliage.
Fix:
- Remove infected lower leaves
- Improve airflow
- Apply fungicide if severe
Lots of small gray spots with dark edges
Septoria leaf spot peppers the lower leaves once the weather turns wet. Remove the marked leaves as soon as they appear, mulch so spores can't splash up, and water at the base instead of over the top.
Fix:
- Remove infected leaves
- Improve air circulation
- Fungicide if severe
Leaves stripped overnight with dark droppings below
A tomato hornworm can clear a branch in a single night. Pick the fat green caterpillars off by hand at dusk. Leave any that carry small white cocoons, since wasps are already taking care of that one.
Fix:
- Hand-pick caterpillars
- Leave any with white wasp cocoons
- Spray Bt if heavy
Flowers yellow and drop without setting fruit
Tomatoes refuse to set fruit when nights stay above 70°F (21°C) or days climb past 85°F (29°C). Keep the plants watered and wait. They start setting again on their own once the weather settles.
Fix:
- Keep plants irrigated
- Wait for favorable temperatures
Cracks ringing or spreading across the fruit
Skins split when a dry spell is followed by a long drink and the fruit swells faster than it can stretch. Steady watering and a layer of mulch even things out. Pick fruit a little early if heavy rain is on the way.
Fix:
- Pick fruit before fully ripe
- Keep watering even
Puckered, scarred fruit at the blossom end
Known as catfacing, this traces back to cold snaps while the flowers were forming. The fruit is still fine to eat. Set transplants out only after the soil has warmed and the worst chill has passed.
Fix:
- No cure for set fruit; remove affected
The oldest leaves near the base turning yellow
A few yellow leaves at the very bottom are often just age, as the plant pours its energy into fruit. If the yellowing climbs or the whole plant looks pale, feed it a balanced fertilizer and check for spots or wilt.
Fix:
- Apply balanced fertilizer if deficient
- Remove diseased tissue
Toxicity
The ripe fruit is good to eat, but the rest of the plant is not. Leaves, stems, and unripe green tomatoes hold a natural compound called solanine that upsets the stomach. Keep the green parts away from pets, livestock, and curious children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People — the ripe fruit
Cats Moderate
Expect drooling, an upset stomach, and low energy. Larger amounts can widen the pupils and slow the heartbeat.
Dogs Moderate
Look for drooling, a poor appetite, an upset stomach, and weakness after a dog chews the leaves or stems.
Horses Moderate
The green parts can bring on an upset stomach, a dull mood, and weakness.
Rabbits Toxic
The leaves and stems hold solanine and aren't safe. Offer only small pieces of ripe fruit as an occasional treat.
Livestock Moderate
Cattle, goats, and sheep can react to the solanine in the foliage with stomach and nervous system trouble.
Birds Caution
The green parts are toxic, so share only ripe fruit and only now and then. Backyard hens can peck a ripe tomato safely.
People Ripe fruit safe
Ripe tomatoes are a kitchen staple and safe to eat. Keep children away from the leaves and green fruit.
Ripe fruit is non-toxic; keep pets away from leaves, stems, and green fruit
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Thousands of tomato varieties exist, but a handful turn up in most gardens. These are the ones worth knowing by name.
Early Girl
An early vining type that hands you ripe slicers in about 60 days, weeks ahead of most.
San Marzano
The classic paste tomato, with long, low seed fruit that cooks down into a deep, rich sauce.
Roma
A compact bush tomato grown for canning and sauce, ripening most of its crop in one tight window.
Celebrity
A dependable all rounder that shrugs off most of the diseases that trouble other tomatoes.
Beefsteak types
Big vining slicers with the fullest flavor, though the heavy fruit splits more than most.
Cherry types
Small, sweet fruit carried in long trusses that keep coming all season, like Sungold and Sweet 100.
Companions
Tomatoes grow best beside herbs and flowers that pull pests away, and worst beside their nightshade cousins, which trade the same diseases back and forth.
Plant near
Basil: Studies show basil can reduce thrips on tomato and intercropping may promote tomato growth
French marigold: Slows glasshouse whitefly population through airborne limonene when planted early in season
Nasturtium: Non-host plant shown to reduce whitefly numbers on tomato
Keep apart
Corn: The corn earworm and tomato fruitworm are the same insect, so the pest builds up on both crops; both are heavy feeders competing for nutrients
Potato: Same Solanaceae family; shares early and late blight, so avoid planting together or in sequence
Pepper: Solanaceous relative sharing tomato diseases; avoid adjacent planting and rotation
Eggplant: Solanaceous relative sharing soilborne diseases and pests with tomato
Black walnut: Roots release juglone; tomatoes are highly sensitive, causing yellowing, wilting, and death near the dripline
How to propagate
Tomatoes are among the easiest plants to multiply, whether you start from a seed packet or take free copies of a plant you already grow.
SeedEasy
Indoors 5-8 weeks before last frost · Germinates 5-10 days at 75-85°F (24-29°C)
Most gardeners start tomatoes from seed. Sow indoors 5 to 8 weeks before your last frost and keep the tray warm, around 75°F to 85°F (24°C to 29°C), and the seedlings break ground in 5 to 10 days. When you move them outside, plant them deep and bury part of the stem, because every buried inch grows fresh roots.
Stem cuttingsEasy
During active growth · Roots in 1-2 weeks in water or moist soil
Tomatoes clone themselves with almost no effort. Snap a healthy sucker off a growing plant, stand it in a glass of water or a pot of moist soil, and it roots within a week or two into a brand new plant, identical to its parent.
Myths
Blossom end rot is cured by adding calcium or crushed eggshells.
The trouble is how the plant moves calcium, not how much sits in the soil. Eggshells take far too long to break down to help, and sprays on the leaves never reach the fruit. Steady, even watering is the real fix.
A handful of Epsom salt makes tomatoes grow bigger and crop heavier.
It does nothing unless your soil is short on magnesium, which is rare. Too much can even make blossom end rot worse by crowding out the calcium the fruit needs.
Water on the leaves in full sun burns them like a magnifying glass.
Droplets dry off long before they could scorch anything. Spotted, scorched leaves trace back to disease, pests, or weather, never to sun shining through a bead of water.
Marigolds keep every garden pest away.
The real effect is narrow. French marigolds do slow whiteflies and may help with a few thrips, but they don't clear out pests in general, and much companion advice rests on garden lore rather than trials.
Pinching off every sucker always gives you more tomatoes.
On the tall vining types, pruning brings bigger, earlier fruit but often a smaller total harvest and more sunscald. On the bushy determinate types, leave the suckers be.
More nitrogen fertilizer means more tomatoes.
Heavy nitrogen grows a lush, leafy plant with little fruit, and it makes the tomatoes you do get more likely to crack. A balanced feed gives you far better results.
Sources
- ASPCA Animal Poison Control
- University of Minnesota Extension
- University of Maryland Extension
- Clemson Cooperative Extension HGIC
- University of Maryland Extension
- Clemson Cooperative Extension HGIC
- Clemson Cooperative Extension HGIC
- University of Minnesota Extension
- Penn State Extension
- University of Minnesota Extension
- PLoS One (peer-reviewed)
- University of Wisconsin-Madison Extension (Wisconsin Horticulture)
- Penn State Extension
- University of Maryland Extension
- University of Illinois Extension
- Penn State Extension